Sound communication system

ABSTRACT

A communication system for an emergency vehicle including a provision for selectively producing plural automatically and manually controlled siren sounds, the sound broadcast of radio reception and the sound amplification of the input to a microphone. A complete momentary-contact, pushbutton console may be employed, if desired, by short circuiting all the inputs to ground except that corresponding to the mode of operation selected. Start up instability is also eliminated. A selector pushbutton performs the dual function of manual siren control. Negative feedback from the speaker is provided selectively for radio and public address sytem use. Common use of components reduces cost and complexity. For example, common use of a voltage controlled oscillator, two amplifier stages, a driver and a speaker assembly is made. Radio input is turned on by an alternate action switch. As described in the specification, the action of &#39;&#39;&#39;&#39;turning on&#39;&#39;&#39;&#39; the radio shorts out all siren functions by firing silicon controlled rectifiers. The microphone input is turned on by pushing the &#39;&#39;&#39;&#39;push to talk&#39;&#39;&#39;&#39; switch thereon. This action fires all the siren shorting silicon controlled rectifiers through a pulse amplifier.

Unite States Patent Carroll [451 Mar. 25, 1975 SOUND COMMUNICATIONSYSTEM [75] Inventor: Gordon S. Carroll, Costa Mesa,

Calif.

[73] Assignee: International Telephone and Telegraph Corporation, NewYork, NY.

[22] Filed: Oct. 29, 1973 [21] Appl. No.: 410,776

[52] US. Cl 340/384 E, 340/384 R [51] Int. Cl. H04q 3/10 [58] Field ofSearch 340/384 R, 384 E [56] References Cited UNITED STATES PATENTS3,747,092 7/1973 Smith 340/384 E Primary E.\'aminerl'larold I. Pitts ty. .d tr rlirm ,A-. D9 dt z [57] ABSTRACT A communication system for anemergency vehicle POWER, SUPPL H CO/VT/QOL, ISSEAABL S including aprovision for selectively producing plural automatically and manuallycontrolled siren sounds, the sound broadcast of radio reception and thesound amplification of the input to a microphone. A completemomentary-contact, pushbutton console may be employed, if desired, byshort circuiting all the inputs to ground except that corresponding tothe mode of operation selected. Start up instability is also eliminated.A selector pushbutton performs the dual function of manual sirencontrol. Negative feedback from the speaker is provided selectively forradio and public address sytem use. Common use of components reducescost and complexity. For example, common use of a voltage controlledoscillator, two amplifier stages, a driver and a speaker assembly ismade. Radio input is turned on by an alternate action switch. Asdescribed in the specification, the action of turning on the radioshorts out all siren functions by firing silicon controlled rectifiers.The microphone input is turned on by pushing the push to talk switchthereon. This action fires all the siren shorting silicon controlledrectifiers through a pulse amplifier.

9 Claims, 17 Drawing Figures SPEAK ER.

M/C/QOPHONE ASSEMBLV F/G. /O

sou/v0 coMMuN/cnT/o/v Sr STEM 8O slsvaleao PATENTEDHARZS 197s SHEET 10Fa 1 SOUND COMMUNICATION SYSTEM BACKGROUND OF THE INVENTION Thisinvention relates to electronic gear for use with loudspeakers, and moreparticularly, to a multipurpose apparatus for use on emergency vehiclesincluding, but not limited to, ambulances and police patrol cars orelsewhere.

In the past, loudspeaker gear for police patrol cars, for example, havebeen complicated and expensive. The number of possible functions thereofhas also been limited.

SUMMARY OF THE INVENTION In accordance with the system of the presentinvention, the above-described and other disadvantages of the prior arthave been overcome by providing means to select one of a plurality ofmodes of operation in a sound communication or other system.

The above-described and other advantages of the present invention willbe better understood from the following detailed description whenconsidered in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings which are to beregarded as merely illustrative:

FIG. I is a block diagram of a sound communication system constructed inaccordance with the present invention;

FIG. 2 is a schematic diagram of a power supply assembly constructed inaccordance with the present invention;

FIG. 3 is a schematicdiagram of a multivibrator hereinafter called anAUTO MV;

FIG. 4 is a schematic diagram of a multivibrator hereinafter called aHI-LO MV;

FIG. 5 is a schematic diagram of a manual control circuit constructed inaccordance with the' present invention;

FIG. 6 is a schematic diagram ofa voltage controlled oscillatorhereinafter referred to as a VCO;

FIG. 7 is a schematic diagram of first and second amplifier stages;

FIG. 8 is a schematic diagram of a driver;

FIG. 9 is a schematic diagram of a speaker assembly;

FIG. 10 is a schematic diagram of a microphone assembly;

FIG. 11 is a schematic diagram ofa control assembly; and

FIGS. 12, 13,14, 15,16 and 17 are graphs ofa group of waveformscharacteristic of the operation of the sound communication system of thepresent invention illustrated in FIGS. 1-11, inclusive.

DESCRIPTION OF THE PREFERRED EMBODIMENT In the drawings, in FIG. 1, asound communication system 20 is shown including a power supply assembly21, an AUTO MV 22, a HI-LO MV 23, a YELP MV 24, a manual control circuit25, a VCO 26, a first amplifier stage 27, a second amplifier stage 28, adriver 29, a speaker assembly 30, a control assembly 31, a radio 32 anda microphone assembly'33.

Power supply assembly 21 has output junctions 56, 58 and 60 shown inFIG. 2 which are maintained at potentials V1, V2 and V3, respectively.Junctions 56, 58

and 60 are connected by leads, not shown in FIG. 1 for clarity, to oneor more of the blocks shown in FIG. 1 other than power supply assembly21.

Power supply assembly 21 has a lead TB1-2 connected to speaker assembly30, leads 14-3, 14-1 and 12-4' connected to control assembly 31, andleads 12-3 and 12-4 connected to microphone assembly 33. Power supplyassembly 21 also has a lead 14-2 connected to driver 29 and a lead 16-11connected to first amplifier stage 27.

The VCO 26 has an output lead 15-1 connected to first amplifier stage27. The VCO 26 has an input lead J3-21 connected from control assembly31.

The AUTO MV 22 has an output lead 13-23 connected to control assembly31.

The HI-LO MV 23 has an output lead 13-22 connected to control assembly31.

The YELP MV 24 has an output lead 13-19 connected to control assembly31.

The manual control circuit 25 has an input lead J3-16 and two outputleads 13-5 and 13-18 connected to control assembly 31.

First amplifier stage 27 has input leads 15-2 and 16- 10B connected fromcontrol assembly 31, and an output lead 51.

A lead J6-10A is connected from microphone assembly 33 to firstamplifier stage 27.

The output lead 51 of first amplifier stage 27 serves as an input leadof second amplifier stage 28. A lead D connects the output of secondamplifier stage 28 to the input of driver 29.

Leads TB2-9 and TB2-10 connect the outputs of driver 29 to speakerassembly 30.

Speaker assembly 30 has output leads P1-13A and P1-13B connected tomicrophone and control assemblies 33 and 31, respectively.

Radio 32 has one side grounded through a resistor 40 and has an outputlead 41 which is connected to control assembly 31.

Power supply assembly 21 is illustrated in FIG. 2 including a relay 51having a winding 52, a pole 53 and a contact 54.

Junctions are provided at 55, 57 and 59 in FIG. 2 in addition tojunctions 56, 58 and 60. A DC. source of potential is provided at 61having a positive terminal 62 and a negative terminal 63. The negativeterminal 63 is grounded at 64. Junctions 59 and 60 are connected fromterminal 63.

A diode 65 is connected from ajunction 66 to a junction 55', and ispoled to be conductive in a direction toward junction 55'. Junctions 55,55 and 56 are connected together. Junctions 57 and 58 are connectedtogether.

A resistor 67 is connected between junctions 55 and 57. A resistor 68 isconnected between junctions 57 and 59. A capacitor 69 is connectedbetween junctions 56 and 58.

Junctions are also provided at 71, 71', 72 and 72. Pole 53 is connectedfrom junction 71. Contact 54 is connected to lead TB 1-2 in speakerassembly 30, shown in FIG. 9.

Junctions 55' and 72 are connected together.

A lead 12-3 is connected from junction 72 to lead 12-3 of microphoneassembly 33 shown in FIG. 10.

A lead 124 is connected from junction 60' to the same lead in FIG. 10. Alead 12-4' is connected from junction 60' to the same lead in FIG. 11.

Junctions and 72 are connected together.

A lead J4-1 is connected from junction 71 to lead J4-1 of controlassembly 31 shown in FIG. 11. Leads 14-2 and 14-3 are connected fromrespective junctions 72' and 71 to respective leads J4-2 and 14-3 in therespective driver 29 and control assembly 31 of FIGS. 8 and 11,respectively. Junctions 71' and 72' are connected together. A dotted box74 includes a potentiometer 75 and a power switch 76. The main power isturned off by opening switch 76. Switch 76 has a pole 77 which isconnected from junction 72, and a contact 78 connected from junction 71.Potentiometer 75 has a winding 79 and a wiper 80. Winding 79 isconnected from junction 60 to potential V3. Movement of potentiometerwiper 80 on winding 79 adjusts the volume which is produced when themicrophone assembly 33 is employed as a combination public addresssystem.

Potentiometer wiper 80 is ganged with pole 77 of switch 76. An outputlead 16-11 is connected from potentiometer wiper 80. Lead 16-11 in FIG.2 is connected to input lead J6-11 of first amplifier stage 27 shown inFIG. 7.

The AUTO MV 22 is illustrated in FIG. 3. The AUTO MV has variousjunctions 82, 83, 84, 85, 86, 87, 88 and 89.

Junctions 82 and 83 are maintained at potential V2. A capacitor isconnected between junctions 82 and 84. A differential amplifier 91 isillustrated in FIG. 3 having inverting and non-inverting input leads 92and 93, respectively.

Amplifier 91 also has positive and nengative power input leads 94 and 95connected to potentials V1 and V3, respectively.

lnverting input lead 92 is connected from junction 84. Non-invertinginput lead 93 is connected from junction 85.

A resistor 96 is shown in FIG. 3 connected between junctions 84 and 86.

Amplifier 91 has an output lead 97 connected to junction 86. Junctions86 and 87 are connected together. A resistor 98 is connected betweenjunctions 85 and 87. A resistor 99 is connected between junctions 83 and85. A resistor 100 is connected between junctions 87 and 88. A capacitor101 is connected from junction 88 to junction 83. Junctions 88 and 89are connected together. A resistor 103 is connected from junction 89 topotential V1. A lead 13-23 is connected from junction 89 to lead 13-23of control assembly 31 shown in FIG. 11.

l-Il-LO MV 23 is shown in FIG. 4 having junctions 104,105,106,l07, 108,109 and 110. Again, an amplifier 111 is provided with inverting andnon-inverting input leads 112 and 113, respectively. Amplifier 111 alsohas a positive power input lead 114 connected to potential V1, and anoutput lead 115 connected to junction 108. A capacitor 116 is connectedbetween junctions 106 and 104. Junctions 104 and 105 are connected topotential V2. The amplifier inverting input lead 112 is connected fromjunction 106. The noninverting input lead 113 is connected from junction107. A resistor 117 is connected between junctions 105 and 107. Aresistor 118 is connected between junctions 107 and 108. A resistor 120is connected betweenjunctions 106 and 108. A resistor 121 is connectedbetween junctions 109 and 110. Junctions 108 and 109 are connectedtogether. A resistor 122 is connected from junction 110 to potential VI.A lead 13-22 is connected from junction 110 to the same lead 13-22 ofcontrol assembly 31 shown in FIG. 11.

Negative power input leads to amplifiers 111. 148 and 180 in FIGS. 4, 6and 7, respectively, may be provided internally or conventionally.

Manual control circuit 25 is shown in FIG. 5 including junctions 123,124, 125, 126, 127, 128 and 129.

A resistor is connected from junction 125 to potential V1. Junctions 123and 124 are connected to potential V2.

As used herein, the phrase Connected to potential is hereby defined tomean connected to a member including, but not limited to, a conductivelead or a conductive junction which has a potential.

In FIG. 5, a resistor Ra is connected from Junction 123 to junction 125.A PNP transistor 134 is provided in FIG. 5 having a collector 135, anemitter 136 and a base 137. A resistor 138 is connected from the base137 of transistor 134 to junction 126, junctions 125 and 126 beingconnected together. A diode 138 is connected between junctions 126 and127 and is poled to be conductive in a direction toward junction 127.

Junctions 127, 128 and 129 are connected together. Transistor emitter136 is connected from junction 128. A resistor 139 is connected betweenjunctions 124 and 129. A capacitor 140 is also connected betweenjunctions 124 and 129.

A lead 15-3 is connected from junction 128 to the same lead 15-3 ofcontrol assembly 31 as shown in FIG. 11.

A resistor 141 and a diode 138 are connected in that order from junction128 to lead 13-15. Lead J3-16 is connected to the same lead 13-16 ofcontrol assembly 31 shown in FIG. 11. Diode 138" is poled to beconductive toward resistor 141. Collector 135 is connected to a lead13-18 through a resistor 142. Lead J3-18 is connected to the same lead13-18 of control assembly 31 shown in FIG. 11.

VCO 26 is illustrated in FIG. 6 having junctions 143, 144, 145 and 146.

A lead 13-21 is connected from the same lead 13-21 of control assembly31 shown in FIG. 11 to junction 143.

Again, amplifier 148 is a differential amplifier. Amplifier 148 isprovided with an inverting input lead 149, a non-inverting input lead150, a positive power input lead 151 and an output lead 152. Invertinginput lead 149 is connected from junction 143. Non-inverting input lead150 is connected to potential V2. Positive power input lead 151 isconnected to potential V1. Junctions 143 and 144 are connected together.A capacitor 153 is connected between junctions 144 and 145. Aunijunction transistor 154 is provided having a first base 155, a secondbase 156 and an emitter 157. transistor emitter 157 is connected fromjunction 144. First base is connected from junction 145. A resistor 158is connected from second base 156 to potential V1.

Junctions 145 and 146 are connected together. A lead 15-1 is connectedfrom junction 146 to the same lead J5-1 of first amplifier stage 27shown in FIG. 7.

The first and second amplifier stages 27 and 28, respectively, are shownin FIG. 7.

First amplifier stage 27 has five input leads J5-1, 16- 10A, J6-10B,16-11 and 15-2, and output lead 51'. Stage 27 has junctions 300, 301,302, 304, 305 and 306. A capacitor 309 and a resistor 310 are connectedin series in that order from lead J5-1 to junction 305. Junctions 304,305 and 306 are connected together. A resistor 81 is connected frominput lead J6-11 to junction 302. Junctions 301 and 302 are connectedtogether. Leads J6-10A and J6-10B are connected to junction 300. Aresistor 311 and a capacitor 312 are connected in series in that orderfrom junction 300 to junction 301. A resistor 313 and a capacitor 314are connected in series in that order from lead J5-2 to junction 302. Acapacitor 315 is connected between junctions 301 and 304.

First amplifier stage 27 also has junctions 163 and 164. Again, firstamplifier stage 27 includes an amplifier 165 with an inverting inputlead 166, a noninverting input lead 167, positive and negative powerinput leads 168 and 169 and an output lead 170.

Inverting input lead 166 is connected from junction 304. Non-invertinginput lead 167 is connected to potential V2. A resistor 171 and acapacitor 172 are connected in parallel between junctions 306 and 163.

Positive and negative power input leads 168 and 169 are connectedrespectively to potentials V1 and V3. Amplifier output lead 170 isconnected to junction 164. Junctions 163 and 164 are connected together.

As stated previously, the first and second amplifier stages 27 and 28,respectively, are connected over lead 51.

Second amplifier stage 28 has various junctions 173, 174, I76 and 177.

A capacitor 178 and a resistor 179 are connected in series from lead 51'to junction 173. Junctions 173 and 174 are connected together. Amplifier180 is provided having an inverting input lead 181, a non-invertinginput lead 182, a positive power input lead 183 and an output lead 184.Non-inverting input lead 182 is connected to potential V2. Invertinginput lead 181 is connected from junction 173. Positive power input lead183 is connected to potential V1. Output lead 184 is connected tojunction 177.

In FIG. 7, second amplifier stage 28 has a resistor 187 and a capacitor188 connected in parallel between junctions 174 and 176. Junctions 176and 177 are connected to a lead D which also connects with the same leadD of driver 29 shown in FIG. 8.

Driver 29 is shown in FIG. 8 including a transformer 189 having aprimary winding 190 and a secondary winding 191. Winding 190 has leads192 and 193. Winding 191 has leads 194 and 195.

Winding lead 192 is connected from lead D which, in turn, is connectedfrom the same lead D of second amplifier stage 28 shown in FIG. 7.

Winding lead 193 is connected to potential V2.

Other various junctions are shown throughout the circuit of FIG. 8including junctions 198, 199, 200, 201, 202, 203 and 204. A resistor 205is connected between junctions 198 and 199. Winding lead 194 isconnected to junction 198. Winding lead 195 is connected to junction200. A resistor 206 is connected between junctions 199 and 200. Junction199 is connected to potential V3. Transistors 207, 208, 209, 210, 211and 211' are shown in FIG. 8.

Transistor 207 has a collector 212 connected tojunction 201, an emitter213 and a base 214 connected from junction 198.

Transistor 208 has a collector 215 connected to junction 201, an emitter216 and a base 217 connected from emitter 213. Junctions 201 and 202 areconnected together. Similarly, junctions 203 and 204 are connectedtogether.

Transistor 209 has a collector 218 connected to junction 202, an emitter219 and a base 220 connected from emitter 216.

Transistor 210 has a collector 221 connected to junction 203, an emitter222 and a base 223 connected from junction 200.

Transistor 211 has a collector 224 connected to junction 203, an emitter225 and a base 226 connected from emitter 222.

Transistor 211 has a collector 227 connected to junction 204, an emitter228 and a base 229 connected from emitter 225.

A lead TB2-10 is connected from emitter 228 to the same lead TB2-10 inspeaker assembly 30 shown in FIG. 9.

A lead 14-2 is connected to junctions 202 and 204 from the same leadJ4-2 of power supply assembly 21 shown in FIG. 2.

A lead TB2-9 connected from emitter 219 is connected to the same leadTB2-9 of speaker assembly 30 shown in FIG. 9.

Speaker assembly 30 is shown in FIG. 9 including junctions 230, 231,232, 233 and 236, junction 236 being grounded.

A lead TB2-9 is connected from the same lead TB2-9 of driver 29, shownin FIG. 8, to junction 230.

A lead TB2-10 is connected from the same lead TB2- 10 of driver 29,shown in FIG. 8, to junction 233.

A resistor 237 is connected between junctions 230 and 231. A resistor238 is connected between junctions 232 and 233.

Transistors 239 and 240 are also provided. Transistor 239 has acollector 242 connected to junction 231, an emitter 241 connected to oneend 251 of a primary winding 249 of a transformer 247. Transistor 239also has a base 243 connected from junction 230, junctions 231 and 232being connected together. A tap on winding 249 is connected to potentialV3.

Transistor 240 includes a collector 245 connected to junction 232, anemitter 244 connected to the other end of winding 249, and a base 246connected to junction 233.

The transformer 247 has a secondary winding 250. Transformer secondarywinding 250 has a lead 253 connected to junction 47 via lead 46, ajunction being provided at 254 which is connected from lead 253 to lead46, and to one side of a speaker 248 over a lead 255.

Secondary winding 250 has its other lead 256 connected to junction 236which is grounded. Junction 236 is connected to the other side ofspeaker 248 over a lead 257. Junction 232 is connected from lead TB1-2of power supply assembly 21 of FIG. 2.

Microphone assembly 33 is shown in FIG. 10 including a double-pole,switch 258.

Switch 258 has poles 259 and 260 and respective contacts 261 and 262therefor.

Pole 259 is connected from lead J6-10A that is connected to the sameinput lead .l6-10A of the first amplifier stage 27 shown in FIG. 7.

Pole 260 is connected from lead J2-3 which is, in turn, connected fromthe same lead 12-3 of power supply assembly 21 shown in FIG. 2.

Contact 261 is connected from negative feedback lead P1-13A which, inturn, is connected from the same lead P1-13A of speaker assembly 30shown in FIG. 9.

A microphone 263 is connected from contact 262 to lead 12-4 which leadis, in turn, connected to the same lead 12-4 of power supply assembly 21shown in FIG. 2.

Control assembly 31, shown in FIG. 11, has input leads 13-23, J3-22,J3-19, 13-18, 15-3, 41, P1-13B, 14-3 and 14-1 connected from the samecorresponding leads in FIGS. 3, 4, 1, 5, 5, 1, 9, 2 and 2, respectively.Control assembly 31 also has output leads J3-21, J5-2, J6-l0B and 13-16connected to the same corresponding leads in FIGS. 6, 7, 7 and 5,respectively.

In FIG. 11, various junctions are shown throughout the circuit ofcontrol assembly 31 including junctions 318, 319, 320, 321, 322, 323,324, 325, 326, 327, 328, 329,330, 331, 332, 333, 334, 335, 336, 337,338,339, 340,341,342, 343, 344, 345, 346, 347, 348, 349, 350, 35l, 352, 353,354 and 355.

Leads 13-23, 13-22 and J3-19 are connected to junctions 318, 319 and320, respectively. A resistor 356 and a diode 357 are connected inseries in that order from junction 318 to junction 321, diode 357 beingpoled to be conductive in a direction toward junction 321. A diode 358is connected between junctions 319 and 321 and poled to be conductivetoward junction 321. A resistor 359 and a diode 360 are connected inseries in that order from junction 320 to junction 322, diode 360 beingpoled to be conductive in a direction toward junction 322. Junctions321, 322 and 323 are connected together. Lead 13-18 is connected tojunction 323. Lead 13-21 is connected from junction 323.

A diode 361 and a resistor 362 are connected in series in that orderfrom junction 318 to potential V1. Diode 361 is connected betweenjunctions 318 and 324, and poled to be conductive toward junction 324.Resistor 362 is connected between junctions 324 and 328. Junction 328 isconnected to potential V1. A diode 363 is connected from junction 319 tojunction 325 and is poled to be conductive in a direction towardjunction 325. A diode 364 is connected from junction 320 to a junction326, and is poled to be conductive in a direction toward junction 326. Adiode 365 is connected from lead 15-3 to a junction 327, and poled to beconductive in a direction toward junction 327. A resistor 369 isconnected between junctions 325 and 329. A resistor 370 is connectedbetween junctions 326 and 330. A resistor 371 is connected betweenjunctions 327 and 330. Junctions 328, 329 and 330 are connectedtogether. A silicon-controlled rectifier 373 has its anode 374 connectedfrom junction 324 and its cathode 375 connected to junction 335.Similarly, silicon-controlled rectifiers 376, 377 and 378 haverespective anodes 379, 380 and 381 connected respectively from junctions325, 326 and 327; and cathodes 382, 383 and 384, respectively, connectedto junctions 336, 337 and 338, respectively, and gates 385, 386 and 387,respectively, connected from junctions 332, 333 and 334, respectively.Silicon-controlled rectifier (SCR) 373 has a gate 388 connected fromjunction 331. A resistor 389 is connected between junctions 331 and 335.A resistor 390 is connected between junctions 332 and 336. A resistor391 is connected between junctions 333 and 337. A resistor 392 isconnected between junctions 334 and 338. Resistors 393, 394, 395 and 396are connected respectively from junctions 331, 332, 333 and 334 tojunctions 344,343, 342 and 342, respectively. Junctions 344 and 349 areconnected together.

Switches are provided at 264, 265, 266, 267 and 268. Each of theswitches enumerated in the last sentence is a momentary contactpushbutton switch. As shown, switch 268 is a single-pole, single-throwswitch. Each of the switches 264, 265, 266 and 267 is a double-pole,double-throw switch. Each of the switches enumerated in the secondpreceding sentence may be identical to the other switches so enumerated,if desired. Some of the details of switch 264 will be described. Thesedetails may also apply to the switches 265, 266 and 267 even though theyare not mentioned in connection therewith herein. Switch 264 has poles397 and 264", and contacts 400 and 264 engageable by poles 397 and 264",respectively. Switch 264 is a break-beforemake switch, as are theswitches 265, 266 and 267. That is, pole 264" always breaks with contact264 before pole 397 engages contact 400.

Switch 265 has poles 401 and 402 engageable with contacts 403 and 404,respectively. Switch 266 has poles 405 and 406 engageable with contacts407 and 408, respectively. Switch 267 has poles 409 and 410 engageablewith contacts 411 and 412, respectively. Switch 268 has a pole 413engageable with a contact 414.

A capacitor 415 is connected from lead 14-3 to junction 349. Poles 397,402, 406 and 410 are connected to junctions 341, 340, 339 and 339,respectively. Junction 341 is maintained at potential V3. Contacts 400,404, 408 and 412 are connected respectively from junctions 338, 337, 336and 335.

Junctions 349, 350, 351, 352, 353 and 354 are connected together. Poles264", 401, 405, 409 and 413 are connected respectively to junctions 354,353, 352, 351 and 350.

Junctions 345, 346, 347 and 348 are connected together from input lead14-1 to contacts 411, 407, 403 and 264, respectively. Contact 414 isalso connected from junction 345.

Control assembly 31 is provided with a transistor 416 having a collector417, an emitter 418 and a base 419. A capacitor 420 is connected fromlead 41 to transistor collector 417. The emitter 418 of transistor 416is connected to junction 355. A resistor 421 is connected from junction355 to potential V3. Lead 15-2 is connected from junction 355.

A double-pole, double-throw switch 270 is also provided. Switch 270 isstable in either one of its positions. That is, it is not a momentarycontact switch. Switch 270 has poles 422 and 423 and contacts 424 and425 engageable thereby, respectively. Switch pole 423 also has a contact425'. Pole 423 is connected to potential V1. Pole 422 is connected frominput lead Pl-l3B from FIG. 9. A resistor 426 is connected fromtransistor base 419 to a junction 500. Junction 500 is connected fromcontact 425. Output lead J6-10B is connected from contact 424.

()ther junctions are shown in FIG. 11 at 501, 502, 503 and 504.Junctions 500 and 501 are connected together. Junction 502 is connectedfrom contact 425' by a resistor 505. A lamp 506 is connected fromjunction 502 to potential V3. A diode 507 is connected between junctions501 and 502 and poled to be conductive in a direction toward junction502. A diode 508 is connected between junctions 501 and 503 and poled tobe conductive in a direction toward junction 503. Junctions 503, 504 and354 are all connected together.

A resistor 509 is connected from lead 12-4 from FIG. 2 to a junction510. A transistor 511 is provided with a collector 512, an emitter 513and a base 514. Base 514 is connected from junction 510. Emitter 513 isconnected to a junction 515. A resistor 516 is connected betweenjunctions 510 and 515, junction 515 being connected to potential V3.

Collector 512 is connected to ajunction 517. A resistor 518 is connectedfrom junction 517 to potential V1. A capacitor 519 is connected betweenjunctions 503 and 517.

Voltage which appears at junction 89 in FIG. 3 is illustrated in FIG.12. Line 316 is zero volts (V3). The fundamental of the waveform of FIG.12 may have a period equal to T In a typical example, T might be 8.0seconds.

The voltage which appears on lead 13-22 shown in FIG. 4 is illustratedin FIG. 13. Line 317 is zero volts. The period T,, of the waveform shownin FIG. 13 may typically be 2.0 seconds.

The YELP MV 24 may be identical to the AUTO MV 22, if desired, with theexception that some circuit values may change so that the YELPequivalent of T will be different from T The voltage which appears onlead 13-19 shown in FIG. 1 at the output of the YELP MV 24 isillustrated in FIG. 14. In this illustration, the fundamental period Tymay be, for example, 0.5 seconds.

Transistor 134, shown in FIG. 5, acts substantially as a switch and ismaintained either at cut-off or at saturation. That is, the transitionfrom cut-off to saturation and vice versa is made very rapidly.

When the button of switch 264 in FIG. 11 is depressed, lead 13-16 inFIGS. and 11 are connected from lead 14-1 in FIGS. 2 and 11 via contact264 and pole 264". The depression of the button of switch 264 will causejunction 128 in FIG. 5 to change in potential as illustrated in FIG. 15from V,,,, to V,,, A voltage directly proportional to that shown in FIG.15 is then applied to the input of the VCO 26 via transistor 134 (FIG.5), resistor 142 FIG. 5), lead 13-18 FIG. 5) and lead 13-21 (FIGS. 6 and11). The frequency of the output signal of VCO 26 will change inaccordance with the solid line waveform shown in FIG. 15.

In general, transistor 134 in FIG. 5 cannot turn on until the voltage ofjunction 128 has risen somewhat. For example, it may rise to a point 293shown in FIG. 15.

In FIG. 15, dotted line 294 may be considered ground or V3, if desired.

When the button of switch 264 in FIG. 11 is no longer depressed, thepotential ofjunction 128 in FIG. 5 may then fall as indicated by thesolid line in FIG. 16. Transistor 134 prevents the VCO 26 from producingan output signal of a frequency below a predetermined minimum. Thefalling potential at 128 in FIG. 5 thus no longer affects the operationof the VCO 26 to the right of point 295 in FIG. '16 because transistor134 is driven to cut-off at point 295.

The output voltage of VCO 26 which can appear at junction 146 in FIG. 6may have a wave shape as shown in FIG. 17.

In order to make the foregoing as clear as possible, it should be statedthat all the functions illustrated in FIGS. 12-17, inclusive, arepotentials which are graphed not necessarily using the same time scales.

In FIGS. 15 and 16, the following relations may or may not be used, asdesired:

ml m3a and The term V may or may not be equal to 12 volts as desired.

At V V and at V the frequency of the output signal of the VCO 26 may ormay not be 500 hertz and 1,500 hertz, respectively, as desired.

The output signal of VCO 26 may be saw-tooth or any other periodic wave.

AUTO MV 22, I-II-LO MV 23 and YELP MV 24 all may be conventionalmultivibrators, or they may be as shown in FIGS. 3, 4 and 3,respectively, with the changes to be noted herein.

In FIG. 2, diode 65 protects all portions of the circuits connected fromjunctions 56, 58 and 60 when battery 61 is connected between terminals62 and 63 with the wrong polarity.

In FIG. 5, when the potential of junction 129 rises above the potentialof junction 126, transistor 134 is driven to saturation. In this state,transistor 134 operates simply as a closed switch.

When the potential of junction 129 falls below the potential of junction126, transistor 134 is cut off and any output signal on lead 13-18 isprevented. In this case, transistor 134 operates as an open switch.

When switch 264 in FIG. 11 is closed, 12 volts, for example, areimpressed upon lead 13-16 in FIG. 5 connected to resistor 141. Capacitorthen charges, and the potential ofjunction 129 rises to a maximum of,for example, 12 volts above line 294 in FIG. 15, i.e., to, for example,

When pole 264 disengages contact 264 in FIG. 11, capacitor 140, in FIG.5, discharges through resistor 139 (see FIG. 16).

In FIG. 6, the input to VCO 26 is supplied over lead 13-21. The outputof VCO 26 is supplied over lead 15-1.

First amplifier stage 27 receives negative feedback over leads 16-10Aand 16-10B. This feedback is added to the other inputs on leads 15-1,16-11 and 15-2 via the arrangement of amplifier 27 including all thosestructures therein, the same forming an analog adder. As statedpreviously, the output of this amplifier stage 27 is connected to theinput of second amplifier stage 28 over a lead 51. Second amplifierstage 28 has an output lead D. See FIG. 7.

First amplifier stage 27 receives negative feedback of lead in two ways.This negative feedback is supplied over leads 16-10A and 16-10B. Thefeedback over lead 16-10A comes from lead Pl-l3A of speaker assembly 30(FIG. 9) through switch 258 shown in FIG. 10.

Negative feedback is supplied over lead 16-103 from lead P1-13B ofspeaker assembly 30 (FIG. 9) to lead P1-13B in control assembly 31 ofFIG. 11 and subsequently to lead 16-10B (FIGS. 7 and 11) through switch270 (FIG. 11).

Leads TB2-l0 and TB2-9 connect the outputs of driver 29 shown if FIG. 8to speaker assembly 30 (FIG. 9). Lead 14-2 is connected from powersupply assembly 21 of FIG. 2.

Driver 29 of FIG. 8 receives an input signal over output lead D ofsecond amplifier stage 28 shown in FIG. 7.

VCO 26 may be entirely conventional or as shown. The same is true offirst and second amplifier stages 27 and 28, respectively, and driver 29and speaker assembly 30.

In FIG. 11, resistors 356 and 359 may be considered, if desired, eitherportions of control assembly 31 shown in FIG. 11, or portions of thecorresponding circuits of AUTO MV 22 and YELP MV 24, respectively. Theconnection of lead 13-18 in FIG. 11 to junction 323, and the connectionsof diodes 357, 358 and 360 to junctions 321, 321 and 322, respectively,in effect, at junction 323, combine the outputs of AUTO MV 22, I'll-LOMV 23, YELP MV 24 and manual control circuit 25 so that they can beimpressed, one at a time, upon the VCO 26 via output lead 13-21 in FIG.11 and the same lead 13-21 in FIG. 6, which lead is the input lead toVCO 26 in FIG. 6.

As will be explained, the potentials of two of the three junctions 318,319 and 320, by switching, will always be maintained at potential V3(ground). This means that the desired signal source whose output isimpressed upon the input of VCO 26 might be loaded or short circuited toground were not diodes 357, 358 and 360 provided. That is the reasonthat these diodes are provided. Resistors 362, 369, 370 and 371 providecurrent to insure that silicon-controlled rectifiers 373, 376, 377 and378 remain fired after they have been fired. Diodes 361, 363, 364 and365 effectively isolate junctions 318, 319 and 320, and lead -3, fromjunctions 324, 325, 326 and 327 when the last named four junctions havepotentials higher than junctions 318, 319, 320 and lead 15-3,respectively.

In FIG. 3, resistor 103 provides a level shift of what otherwise wouldbe the output signal of the AUTO MV 22 which would appear at junction 88so that all portions of the waveform thereof are at amplitudes greaterthan zero volts. The same is true of resistor 122 in FIG. 4. The same istrue of all signals appearing on output lead 13-21 in FIG. 11 under allpossible modes of operation.

In FIG. 11, resistors 389, 390, 391 and 392 keep the leakage currentsthrough respectively siliconcontrolled rectifiers 373, 376, 377 and 378from firing them, respectively.

If desired, switch 270 may be an entirely conventional alternate actionpushbutton switch. That is, it may have a button which when pushed oncecauses the switch to change to one position, and when pushed twicecauses it to change to the other position thereof. Alternatively, switch270 may be a pushbutton switch having two buttons, one button for oneposition of the switch and one button for the other position thereof. Inthis case, the buttons are mechanically connected so that depressing onebutton causes the other button to be projected outwardly toward theoperator and vice versa.

Resistors 393, 394, 395 and 396 are employed to limit the gate currentsof the respective siliconcontrolled rectifiers 373, 376, 377 and 378.

The depression of the pushbutton corresponding to one of the switches264, 265, 266 and 267 causes a respective one of the silicon-controlledrectifiers 378, 377, 376 and 373 to be cut off while the others arefired. This causes three or four of junctions 320, 319 and 318,respectively, to be short circuited to ground (V3). The other one is oris not short circuited depending upon whether or not switch 268 isactuated or not, respectively.

In the case of each of the silicon-controlled rectifiers 373, 376, 377and 378, the manner of providing a short circuit or an open circuit isthe same. For both of these possibilities, only the operation of thesiliconcontrolled rectifiers produced by depressing switch 265 will bedescribed in detail.

When the pushbutton of switch 265 is depressed, pole 401 will engagecontact 403 and an operating voltage supplied over lead 14-1 will beconnected to the gates of the silicon-controlled rectifiers from lead14-1 via contact 403, pole 401, junction 353, junction 352, junction351, junction 350, junction 349 and through resistors 393, 394, 395 and396 from respective junctions 344, 343 and 342, junction 342, the lastfour junctions enumerated being connected from junction 349. In thismanner, three of the four silicon-controlled rectifiers will firebecause those corresponding to switches 264, 266 and 267 still havetheir poles 397, 406 and 410 in engagement with the respective contacts400, 408 and 412. The poles of the switches 264, 266 and 267 andcontacts 400, 408 and 412 thus act as three normally closed switchesthrough which the corresponding silicon-controlled rectifiers are fired.However, so long as pole 401 is in engagement with contact 403 of switch265, as stated previously, pole 402 will not be in engagement withcontact 404 and silicon-.

controlled rectifier 377 cannot fire because the cathode circuit thereofis opened by movement of pole 402 out of engagement with contact 404.

Switch 268 in FIG. 11 is operable to turn the siren off. That is, movingpole 413 of switch 268 into engagement with contact 414 will, when allthe pushbuttons corresponding to switches 264 and 267 are not pushed,fire all of the silicon-controlled rectifiers because all of the poles397, 402, 406 and 410 will lie in engagement with their respectivecontacts 400, 404, 408 and 412. What is meant by a manual squelch isthat, at whatever the condition of the operation of the manual controlcircuit 25 of FIG. 5 when the pushbutton of switch 268 is depressed, theaudio output of speaker 248 shown in FIG. 9 will immediately be reducedto zero.

It is not always easy to control the operation of the system 20, and itsindividual components and subcomponents thereof because of transientconditions which can occur when switch 76 in FIG. 2 is first closed.That is the reason for the connection from lead 14-3 in FIG. 2 to thecapacitor 415 in FIG. 11, and the reason for the use of capacitor 415 inFIG. 1 1. Closure of switch 76 causes a spike to be impressed uponjunction 349 in FIG. 11 through capacitor 415 which, when the switches264-267 are in the positions shown in FIG. 11, causes all four of thesilicon-controlled rectifiers to fire.

In FIG. 11, transistor 416 operates as a switch which is essentiallyclosed when pole 423 of switch 270 engages contact 425. This passes theradio input on lead 41 to the first amplifier stage 27 in FIG. 7 vialead 15-2. At the same time, negative feedback is supplied to firstamplifier stage 27 from lead P1-13B which is connected to pole 422 ofswitch 270 in FIG. 11, the connection to first amplifier stage 27 beingmade by switch 270 when pole 422 engages contact 424 and sends thefeedback signal to the first amplifier stage 27 in FIG. 7 over lead16-10B. This feedback signal is desirable to reduce the amplitude of theaudio output of speaker 248 when the switch of transistor 416 is closed.

In a similar manner, feedback is supplied to the first amplifier stage27 when switch 258 in FIG. is moved from the position shown to aposition where poles 259 and 260 engage contacts 261 and 262,respectively. In this case, negative feedback is supplied to contact 261over lead Pl-13A and to lead .I6-l0A of FIGS. 7 and 10 through pole 259shown in FIG. 10.

In FIG. 11 lamp 506 is fully brilliant when pole 423 engages contact425. Lamp 506 has reduced brilliance when pole 423 engages contact 425'.Diode 507 keeps transistor 416 from being fiired and the SCRs from beingfired when pole 423 engages contact 425'. Diode 508 keeps lamp 506 frombeing illuminated and transistor 416 from being fired when junction 349is att a high potential.

When pole 423 engages contact 425, all of the SCRs are tired via diode508.

When pole 260 engages contact 262 in FIG. 10, the transient voltagethereby created impressed a pulse on junction 503 via capacitor 519which fires all of the SCRs. Transistor 511 in FIG. 11 and the circuitadjacent thereto forms a pulse amplifier 520 which amplities thetransient voltage.

OPERATION The system of FIG. 1 operates as follows. In the first place,switch 76 in FIG. 2 is closed to supply power. A spike is thentransmitted to junction 349 in FIG. 11 to fire all four of thesilicon-controlled rectifiers. VCO 26 then does not receive any inputsignal over lead 13-21 shown in FIG. 11. A signal will then be supplieddepending upon which pushbutton of the switches 264267 is depressed.Depressing one pushbutton will cause the outputs of three of the boxes22, 23 and 24 shown in FIG. I to be short circuited to ground. Theoutput not short circuited will or will not be passed over lead 13-21from FIG. 11 to the input of VCO 26 shown in FIGS. 1 and 6 dependingupon whether switch 264 was operated.

If switch 264 is operated, only the manually controlled siren sound willbe produced. Otherwise, the AUTO, HI-LO or YELP siren sound will beproduced.

Should switch 264 be actuated and then deactuated, the audio output ofspeaker 248 may be suppressed simply by placing pole 413 of switch 268in engagement with contact 414 thereof. In this manner, the audio outputof speaker 248 may be controlled selectively to provide an outputcorresponding to the outputs of boxes 22, 23, 24 and shown in FIG. 1.

Should it be desirable to connect the output of radio 32 in FIG. I tothe input of first amplifier stage 27 in FIG. 7, this may be done bymoving switch 270 in FIG. 11 to a position opposite that shown in FIG.11. This will cause transistor 416 to act as a closed switch, andthrough pole 422 and contact 424 of switch 270, connect negativefeedback from speaker assembly 30 of FIG. 9 over lead P1-l3B to leadJ6-l0B of FIGS. 7 and 11.

Microphone assembly 33 may be employed by moving poles 259 and 260 intoengagement with respective contacts 261 and 262 shown in FIG. 10.

When the output of AUTO MV 22 is being impressed upon VCO 26, speaker248 will produce an electronic siren sound which is in common use today.

When the signal being delivered to the input of VCO 26 is the output ofYELP MV 24, speaker 248 produces a sound which is commonly used on boardship in the US Navy to signal to signal an emergency.

When the outputu signal of I-II-LO MV 23 is being impressed upon theinput of VCO 26, speaker 248 produces a sound which is commonly used onemergency vehicles in European countries.

A number of portions of this disclosure may be identical to respectiveportions of copending application Ser. No. 384,889 filed Aug. 2, 1973,by G. S. Carroll for SOUND COMMUNICATION SYSTEM.

Some of the prior art related to the field of the present invention, butnot to the invention per se, includes US. Pat. No. 3,137,846. Otherprior art includes Electronic Design 20, Sept. 27, 1967.

If desired, all the multivibrators disclosed herein may be conventionalor of a type and for use with operational amplifiers identical herein asdifferential amplifiers disclosed in the book Operation al Amplifiers byL. P. I-Iullsman (McGraw-Hill Book Co., 1971).

From the foregoing, it will be appreciated that the adjustment ofpotentiometer in FIG. 2 does not adjust the radio volume but adjust onlythe public address system volume. If desired, potentiometer 75 in FIG. 2may be turned to produce the lowest volume possible during use of thesystem 20 as a system other than a public address system when switch 76in FIG. 2 is closed.

None, one, two or three of V,,, V and V in FIG. 15 may or may not bedifferent from V,,,,, V,,, and V,,,;,, respectively, shown in FIG. 16,and vice versa.

The phrases power supply" and power supply assembly" are hereby definedfor use herein and for use in all the claims to mean a power supply thatmay or may not include a battery or the like.

The phrase means to provide DC. power is hereby defined herein and foruse in all the claims to mean either a DC. source of potential, anequivalent thereof or merely two conductive leads.

Preferably, radio 32, shown in FIG. 1, is grounded through resistor 40.This ground preferably is the same chassis ground that is provided fromterminal 63 in FIG. 2 at 64 and from winding 52 of relay 51 in FIG. 2.

As stated previously, VCO 26, shown in FIG. 6, may provide an outputsignal which may or may not be a saw-tooth. In any event, the frequencyof the output signal of VCO 26 which appears on output lead JS-ltherefrom, as shown in FIG. 6, can follow, as is well known, theamplitude of the input voltage input thereto supplied over lead J3-21.This following action may be faithful or approximate. However, normally,the output signal of VCO 26, is as shown in FIG. 6, the frequency ofwhich preferably is approximately proportional to the magnitude of theinput voltage to the VCO 26.

The phrase means connecting, as used herein and as used in all theclaims in any of its grammatical forms, is hereby defined to include anyone or more of: a resistor, a diode, any transistor, any switch, anyconductor or any other component, or otherwise.

The phrase ramp voltage is hereby defined for use herein and for use inall the claims to mean either a voltage which increases at least over aportion thereof for a predetermined time interval, or a voltage whichdecreases at least over a portion thereof during a predetermined timeinterval. The phrase ramp voltage" is hereby further defined for useherein and for use in the claims to mean a ramp voltage which is eitherlinear or non-linear during the times that the ramp thereof isincreasing or decreasing.

Diode 65, shown in FIG. 2, may be shorted out and omitted in some cases,if desired.

The phrase in series is hereby defined for use herein and for use in allthe claims to mean in any order.

The word energized, as describing a power supply or power supplyassembly 21 herein and in all the claims, is hereby defined as acondition of power supply energization including, but not limited to,when battery 61, shown in FIG. 2, is connected in power supply assembly21 as shown in FIG. 2.

Switch 268 in FIG. 11 may also be considered to be a SIREN OFF switch.

While the button of switch 264 is depressed, the tone which can be heardover speaker 248 in FIG. 9 will rise in pitch in the manner such as isillustrated in FIG. 15. When the pushbutton switch 264 is released, thepitch of the sound emanating from the speaker 248 will follow the curveof FIG. 16. However, the pitch of the sound will not fall below point295 in FIG. 16.

In FIG. 11, junctions 318, 319 and 320 may be considered to be theoutput junctions of AUTO MV 22, HI-LO MV 23 and YELP MV 24,respectively, if desired. In FIG. 5, junction 128 may be considered tobe the output junction of manual control circuit 25 because transistor135 acts merely as a switch.

Resistor 356 and diode 357, diode 358, resistor 359 and diode 360, theemitter-collector circuit oftransmitter 134 and/or other portions of themanual control circuit 25 and resistor 142 (FIGS. and 11) may bedescribed as including, but not limited to, means actuable effectivelyto disconnect or to produce effectively an open circuit betweenrespective junctions 318, 319 and 320 and lead J3-=18 (FIG. 11), and VCOinput lead 13-21 shown in FIGS. 6 and 11 when the respective junctions318, 319, 320 and lead J5-3 are short circuited to ground, such meansalso being actuable effectively to connect or to produce effectively aconductive path through the respective means when one of the otherofjunctions 318, 319, 320 and lead J5-3 is short circuited to ground.

What is claimed is:

l. A multipurpose sound communication system comprising: first andsecond D.C. voltage sources having first and second output leads,respectively, connected to first and second output junctions,respectively, said first and second sources being adapted to producerespective first and second output signals on said first and secondleads thereof, respectively, said first and second signals having firstand second respec tive first and second magnitudes which are functionsof time different from each other; a voltage controlled oscillator VCO)having an input lead and an output lead, said VCO being adapted toproduce an output signal on said output lead thereof having at least anAC. of an audio frequency controlled in accordance with the magnitude ofthe input signal applied to the said input lead thereof; first andsecondconnection means connected from said first and second outputjunctions, respectively, to said VCO input lead, said first connectionmeans being actuatable to produce effectively an open circuit betweensaid first source output junction and said VCO input lead when saidfirst source output junction is short circuited to ground, said firstconnection means being actuable to produce effectively a conductive pathbetween said first source output junction and said VCO input lead whensaid first source output junction is not short circuited to ground, saidsecond con- 5 nection means being actuable to produce effectively anopen circuit between said second source output junction and said VCOinput lead when said second source output junction is short circuited toground, said second connection means being actuable to produceeffectively a conductive path between said second source output junctionand said VCO input lead when said second source output junction is notshort circuited to ground; manually actuable means connected from saidfirst and second output junctions, respectively, to ground, saidmanually actuatable means being selectively operable to short circuitone but not the other of said first and second output junctions toground; and output means having an input lead connected from said VCOoutput lead for broadcasting audible sound in accordance with theamplitude and frequency of said VCO output signal component on said VCOoutput lead.

2. The invention as defined in claim 1, wherein said manually actuablemeans has a first common input lead adapted to receive pulses toestablish all of said short circuits selectively, a second common inputlead for connection from a source of an approximately constant D.C.voltage, and a main power switch and a capacitor connected in seriesbetween said first and second com- 30 mon input leads.

3. The invention as defined in claim 1, wherein one of said first andsecond connection means includes a diode poled to be conductive in adirection toward said VCO input lead.

4. The invention as defined in claim 3, wherein the other of said firstand second connection means also includes a diode poled to be conductivein a direction toward said VCO input lead.

5. The invention as defined in claim 3, wherein the other of said firstand second connection means includes a series connected transistorswitch.

6. The invention as defined in claim 1, wherein said manually actuablemeans includes first and second circuits, and first and second manuallyactuably momentary contact double-pole, double-throw switch means; saidfirst and second circuits having third and fourth junctions,respectively, fifth and sixth junctions, respectively, seventh andeighth junctions, respectively, first and second diodes, respectively,first and second resistors, respectively, third and fourth resistors,respectively, fifth and sixth resistors, respectively, and first andsecond silicon-controlled rectifiers, respectively; said first diodebeing connected from said first output junction to said third junctionand being poled to be conductive toward the latter; said second diodebeing connected from said second output junction to said fourth junctionand being poled to be conductive toward the latter; said first andsecond resistors being respectively connected from said third and fourthjunctions to an approximately constant potential conductor; said firstand second silicon-controlled rectifiers having first and second anodes,respectively, first and second cathodes, respectively, and first andsecond gates, respectively; said first and second anodes being connectedfrom said third and fourth junctions, respectively; said first andsecond cathodes being connected to said fifth and sixth junctions,respectively; said first and second gates being connected from saidseventh and eighth junctions, respectively; said third and fourthresistors being respectively connected from said seventh and eighthjunctions to said fifth and sixth junctions, respectively; a commonlead; said fifth and sixth resistors being connected respectively fromsaid seventh and eighth junctions to said common lead; said first andsecond switch means including first and second normally closed switches,respectively, and first and second normally open switches, respectively;said first switch means normally open switch being connected between anapproximately constant potential conductor and said common lead; saidsecond switch means normally open switch being connected in parallelwith said first switch means normally open switch; said first switchmeans switches being ganged in a manner such that said normally closedswitch thereof makes after said normally open switch thereof breaks;

said second switch means switches being ganged in a manner such thatsaid normally closed switch thereof makes after said normally openswitch thereof breaks; said first and second switch means normallyclosed switches being respectively connected from said fifth and sixthjunctions to ground.

7. The invention as defined in claim 6, wherein one of said first andsecond connection means includes a diode poled to be conductive in adirection toward said VCO input lead.

8. The invention as defined in claim 7, wherein the other of said firstand second connection means also includes a diode poled to be conductivein a direction toward said VCO input lead.

9. The invention as defined in claim 7, wherein the other of said firstand second connection means includes a series connected transistorswitch.

1. A multipurpose sound communication system comprising: first andsecond D.C. voltage sources having first and second output leads,respectively, connected to first and second output junctions,respectively, said first and second sources being adapted to producerespective first and second output signals on said first and secondleads thereof, respectively, said first and second signals having firstand second respective first and second magnitudes which are functions oftime different from each other; a voltage controlled oscillator (VCO)having an input lead and an output lead, said VCO being adapted toproduce an output signal on said output lead thereof having at least anA.C. of an audio frequency controlled in accordance with the magnitudeof the input signal applied to the said input lead thereof; first andsecond connection means connected from said first and second outputjunctions, respectively, to said VCO input lead, said first connectionmeans being actuatable to produce effectively an open circuit betweensaid first source output junction and said VCO input lead when saidfirst source output junction is short circuited to ground, said firstconnection means being actuable to produce effectively a conductive pathbetween said first source output junction and said VCO input lead whensaid first source output junction is not short circuited to ground, saidsecond connection means being actuable to produce effectively an opencircuit between said second source output junction and said VCO inputlead when said second source output junction is short circuited toground, said second connection means being actuable to produceeffectively a conductive path between said second source output junctionanD said VCO input lead when said second source output junction is notshort circuited to ground; manually actuable means connected from saidfirst and second output junctions, respectively, to ground, saidmanually actuatable means being selectively operable to short circuitone but not the other of said first and second output junctions toground; and output means having an input lead connected from said VCOoutput lead for broadcasting audible sound in accordance with theamplitude and frequency of said VCO output signal component on said VCOoutput lead.
 2. The invention as defined in claim 1, wherein saidmanually actuable means has a first common input lead adapted to receivepulses to establish all of said short circuits selectively, a secondcommon input lead for connection from a source of an approximatelyconstant D.C. voltage, and a main power switch and a capacitor connectedin series between said first and second common input leads.
 3. Theinvention as defined in claim 1, wherein one of said first and secondconnection means includes a diode poled to be conductive in a directiontoward said VCO input lead.
 4. The invention as defined in claim 3,wherein the other of said first and second connection means alsoincludes a diode poled to be conductive in a direction toward said VCOinput lead.
 5. The invention as defined in claim 3, wherein the other ofsaid first and second connection means includes a series connectedtransistor switch.
 6. The invention as defined in claim 1, wherein saidmanually actuable means includes first and second circuits, and firstand second manually actuably momentary contact double-pole, double-throwswitch means; said first and second circuits having third and fourthjunctions, respectively, fifth and sixth junctions, respectively,seventh and eighth junctions, respectively, first and second diodes,respectively, first and second resistors, respectively, third and fourthresistors, respectively, fifth and sixth resistors, respectively, andfirst and second silicon-controlled rectifiers, respectively; said firstdiode being connected from said first output junction to said thirdjunction and being poled to be conductive toward the latter; said seconddiode being connected from said second output junction to said fourthjunction and being poled to be conductive toward the latter; said firstand second resistors being respectively connected from said third andfourth junctions to an approximately constant potential conductor; saidfirst and second silicon-controlled rectifiers having first and secondanodes, respectively, first and second cathodes, respectively, and firstand second gates, respectively; said first and second anodes beingconnected from said third and fourth junctions, respectively; said firstand second cathodes being connected to said fifth and sixth junctions,respectively; said first and second gates being connected from saidseventh and eighth junctions, respectively; said third and fourthresistors being respectively connected from said seventh and eighthjunctions to said fifth and sixth junctions, respectively; a commonlead; said fifth and sixth resistors being connected respectively fromsaid seventh and eighth junctions to said common lead; said first andsecond switch means including first and second normally closed switches,respectively, and first and second normally open switches, respectively;said first switch means normally open switch being connected between anapproximately constant potential conductor and said common lead; saidsecond switch means normally open switch being connected in parallelwith said first switch means normally open switch; said first switchmeans switches being ganged in a manner such that said normally closedswitch thereof makes after said normally open switch thereof breaks;said second switch means switches being ganged in a manner such thatsaid normally closed switch thereof makes after said normally openswitch thereof breaks; said first and second swiTch means normallyclosed switches being respectively connected from said fifth and sixthjunctions to ground.
 7. The invention as defined in claim 6, wherein oneof said first and second connection means includes a diode poled to beconductive in a direction toward said VCO input lead.
 8. The inventionas defined in claim 7, wherein the other of said first and secondconnection means also includes a diode poled to be conductive in adirection toward said VCO input lead.
 9. The invention as defined inclaim 7, wherein the other of said first and second connection meansincludes a series connected transistor switch.